Mahofst,
I cannot answer for David. But here are my answers to the questions you pose.
How to protect yourself from liable:
First, understand it, and then understand what a SLAPP suit is.
http://www.thefirstamendment.org/antislappresourcecenter.html
Then dont say anything you do not know is true. Sure I am annonymous, but for me that is more of a point about truth in profiles. I can be almost anyone and use almost any email address to back it up, I can use a fake picture and admin's will never be the wiser. Admin's tracking people only care about one thing, your mac address and your IP address, and if you want to you can make those up too...Your credibility online is more about what you post than what nick you go by, if they want you for libel, they can find you regardless of identity you choose to use.
I personally asked every possible question and tried to keep the company on a legal track when it first presented itself. Instead this company chose to lie, about it's affiliations, it's board of directors, not provide financials, not get registered with the federal and state agencies it should, chose not to provide the service it promised, and so on.
Then the threats came against those that questioned the business and it's owner.
Does that sound like a situation where you need to fear libel?
Posting the companies own responses, links to other peoples accounts, government actions, and the companies own documents just does not constitute libel.
Even if it did, if it is a scam to begin with (which you should be sure, because whatever identity you represent yourself with online, they can still find you..see above H/W address and IP), they do not want to sue you.
Why??
If they sue you, you are allowed legally to defend yourself with discovery of their information... You get to request their financials, all their records, everything, and because they filed suit, you are then entiteled to it all. Then you also get to file counter suit for the SLAPP...
Scammers will threaten with libel suits to shut you up, but never file because they know you will get them in discovery.
just my 2 cents